#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;

class Solution {
public:
    vector<vector<int>> fourSum(vector<int>& nums, int target) {
        sort(nums.begin(), nums.end());
        vector<vector<int>> ret;
        int n = nums.size();
        for (int i = 0; i < n;) {
            for (int j = i + 1; j < n;) {
                int left = j + 1, right = n - 1;
                long long k = (long long)target - nums[i] - nums[j];

                while (left < right) {
                    int sum = nums[left] + nums[right];
                    if (sum > k) {
                        right--;
                    }
                    else if (sum < k) {
                        left++;
                    }
                    else {
                        ret.push_back(
                            { nums[i], nums[j], nums[left], nums[right] });
                        left++;
                        right--;
                        while (left < right && nums[left] == nums[left - 1]) {
                            left++;
                        }

                        while (left < right && nums[right] == nums[right + 1]) {
                            right--;
                        }
                    }
                }

                j++;
                while (j < n && nums[j] == nums[j - 1]) {
                    j++;
                }
            }

            i++;
            while (i < n && nums[i] == nums[i - 1]) {
                i++;
            }
        }

        return ret;
    }
};

int main()
{
	return 0;
}